In recent years, a secondary battery has been used as power sources of electronic devices, such as notebook-type personal computers and cellular phones, and moreover a development of hybrid vehicles and electric vehicles employing the secondary battery as power sources for the purpose of reducing the environmental loads has been advanced. For the power sources thereof, a secondary battery having a high energy density, a high voltage, and high durability has been demanded. A lithium ion secondary battery has drawn attention as a secondary battery capable of achieving a high voltage and a high energy density.
The lithium ion secondary battery contains members of a cathode, an anode, an electrolyte, and a separator, in which the cathode contains a cathode active material, a conductive auxiliary, a collector, and a binder. As the binder, fluorine-based resin such as polyvinylidene fluoride and polytetrafluoroethylene, a styrene-butadiene copolymer, and an acrylic copolymer have been used (for example, Patent Documents 1 to 3).